The only problem was that the PCIe interface was dedicated to the USB 3.0 controller; but that’s nothing a hot-air rework station couldn’t fix. We’ve previously seen steady-handed hackers ...

This showed that the Raspberry Pi would happily talk with a VL805-based USB 3.0 PCIe expansion card, as well as a Realtek RTL8111-based Ethernet card, but not a number of other PCIe cards.